1. Field of Invention
This invention relates to a binding machine for binding bar-shaped materials such as iron reinforcing rods with a binding wire of metal.
2. Description of Prior Art
A binding machine of this type has been disclosed by Examined Japanese Patent Publication No. Sho. 59-39027 or Unexamined Japanese Utility Patent Publication No. Hei. 4-40686. The binding machine is designed as follows: A binding wire of metal is fed out of a binding machine body by a wire feeding mechanism while being curved, so that it is looped around articles such as bar-shaped materials to be bound, to bind them together. At the end of the binding machine body, a bend guide member is provided which is curved substantially semi-circularly to curve the wire while receiving it from the binding machine body. Hence, the wire fed out of the binding machine body is looped around the articles set inside the bend guide member while being curved along the bend guide member; that is, a wire loop is formed around the articles. A part of the wire loops thus formed is twisted with a twisting hook, so that the wire loop is forcibly decreased in diameter to bind the articles together.
In the binding operation, it is necessary to set the articles inside the bend guide member as was described above. However, to do so is rather troublesome, because of the structure of the bend guide member. That is, the bend guide member is curved substantially semi-circularly as was described above, thus obstructing the movement of articles at the front. Hence, in setting the articles inside the bend guide member, they are liable to strike the end portion of the bend guide member, thus impeding the binding operation.
On the other hand, it is necessary to change the diameter of the wire loop depending on the total diameter of articles to be bound. As the diameter of the wire loop changes, the position where the twisting hook holds the wire loop is shifted (hereinafter referred to as "a loop holding position", when applicable). Moving the twisting hook to a plurality of loop holding positions to hold the wire loops different in diameter makes the binding machine intricate in structure, and increases the weight of the latter. Thus, the movement of the twisting hook to the plurality of loop holding position is not practical. Hence, in practice, a relatively large wire loop is formed for all of the total diameters of articles, and the number of twists of the wire loop is adjusted according to the total diameter of the given articles. That is, in the case where the articles to be bound is large in total diameter, the number of twists is decreased; that is, the twisted part of the wire loop is decreased in length; whereas in the case where the articles to be bound is small in total diameter, the number of twists is increased; that is, the twisted part of the wire loop is increased in length. However, the adjustment of the number of twists in the above-described manner is disadvantageous in that, especially in binding articles small in total diameter, the wire and the wire twisting energy are not economically used. That is, the adjustment is low in efficiency.